Composite abrasive element



t 'July/.7, 1942. y N. HOLMSTEN 2,288,624

I l COliPOSITE ABRASIVE ELEMENT Filed July T'L, 1939 @l PatentedrJuly 7, 1942 UNITED lSTATES PATENT oFFlcE 2,238,624 y coMPosrrE ABRAsrvE ELEMENT Niilo Holmsten, New Rochelle, N. Y.

Application July 1, 1939, Serial No. 282,337

12 Claims.

'Ihis invention relates to anabrasive element, and more particularly to a composite abrasive element. Y

The nature and objects of the instant invention will become clear from the following description, appended claims, and accompanying drawing forming a part of this specification and wherein: l

Figure 1 is a top plan view of one form of the composite abrasive element constituting the in stant invention;

Figure 2 is a section taken on the line 2-2 of Figure 1; y T

Figure 3 is an enlarged elevation, partly broken away, of one embodiment of a backing of the composite abrasive element; and

Figure 4 is an enlarged elevation, partly v broken away, of another embodiment of a backduring use, either under dry or wet conditions.

AIn the preferred embodiment, the composite abrasive element consists essentially of a sheet material, preferably fibrous, having abrasive grits adhesively secured to one surface thereof and the other (opposite) surface adhesively secured to a ply-wood backing. The fibrous sheet material and the ply-wood backing are coextensive The ply-Wood backing is an essential feature of the instant invention, and the composite abrasive element, by virtue thereof, possesses the aforementioned characteristics. The ply-wood constituting thebacking may be formed of any number of wood plies. Satisfactory results have been obtained when the backing consists of a one, two or three-ply ply-wood. Though the ply-wood backing, when it consists of a plurality of plies, may be constructed in the usual manner with the` grains of the plies parallel to each other, I have found that surprising and unexpected results, particularly with respect to the previously mentioned properties. are obtained when the ply-Wood backing is constructed so that the grain of each of the plies is angularly dis- The composite abrasive element is.

posed with respect to the other. The preferred angular disposition of the grain of the plies with respect to each other depends on the number of plies constituting the backing.

In that embodiment of the invention which utilizes a ply-wood backing consisting of two plies, though the plies may be disposed with respect to each other so that the grain of one ply is at any angle with respect to the other, best results are secured when the grain of one of the plies is disposed at approximately right angles to the grain of the other ply.

In that embodiment of the invention which utilizes three plies, though the plies may be so disposed that the -grain'of each ply is at any angle with respect to the others, best results are obtained' when the three plies are so arranged that in the final ply-wood the grains of adjacent no separation of the component parts thereof c plies are disposed at anvangle of approximately with respect to each other.

The ply-wood backing may be made of any appropriate wood. I have found that satisfactory results are secured in the two-ply construction whenone ply is formed of poplar and the other of gum wood. In the three-ply embodiment, Il

have secured satisfactory results when the plies are formed of birch or maple, or when two of the. plies are formed of birch or maple,`and the remaining ply formed of the other.

The thickness of the backing, of course, de#

heat, through the medium of any adhesive em-V ployed in the manufacture of ply-Wood.

Any abrasive grit may .be used. Emery, silicon carbide, garnet, aluminum oxide, etc. are illustrative examples of abrasive grits which may be used. 'I'he size of the grains of the abrasive grit may vary from ne to coarse, depending on the intended use of the product.

The abrasive grit is adhesively secured to the fibrous-sheet material through the medium of any well-known adhesive. This adhesive may be either the Water-soluble or water-insoluble type,

as desired. The sheet material to which the abrasive grit and the ply-wood backing are ading to thesheet material is one which sets to form a firm, flexible bond. The bond is sufficiently strong and rigid so that it will flex and not break or separate during the intended use of the product.' Bakelite adhesives,'tapioca adhesives and animal glues may be mentioned as illustrative examples of adhesives which have given satisfactory results in adhesively securing the backing to the sheet material.

In order to more fully explain the nature of the invention, the embodiment thereof which relates to abrasive discs of the type and nature which are secured to grinding heads will now be described.

Referring now to the drawing, wherein an abrasive disc of the previously mentioned type is illustrated, and wherein like reference numerals designate like parts, the reference numeral I designates generally the composite abrasive disc which comprises 'theply-wood backing 2 to which a sheet material (fabric) 3 is adhesively secured by means of an adhesive 4 of the type and nature previously described. On the free surface of the fabric, an abrasive grit 5 is adhesively secured by means of an adhesive 6, also previously described.

The abrasive disc I is provided with a central aperture or opening 1, whereby said disc may be mounted on a grinding head. To facilitate the mounting of the abrasive disc I on the grinding head there is provided a pair of diametrically opposed slots 8. As shown in the drawing, one end of each slot 8 communicates with the central opening 1, the opposite end vof each slot 8 being provided with a. circular hole 9 whereby, when the disc is mounted on the grinding head, the slots will not be ripped beyond their' desired termini.

Referring now to Figure 3, it will be noted that in the form shown therein the backing is composed of two plies I0 and I2 adhesively se- -cured together through the medium of the selected adhesive (not. shown). It is to be noted that in this embodiment the plies l0 and I2 are so arranged and disposed with. respect to each I5 of the ply I5 is disposed atan angle of apl proximately 60 with respect to the grain I6 of the ply I6 and that the grain I1 of ply I1 is disposed at an angle of approximately 60 with respect to the grain I6'. In other words, in the three-ply embodiment, the angularity between the grains in adjacent plies is approximately 60.

In producing the abrasive disc, one surface of the selected sheet material 3 is rendered tacky with the chosen adhesive, and the abrasive grit applied thereto, as is well known in the art. Thereafter, the selected adhesive is applied to the opposite surface of the sheet material or to the. top surface of -the ply-wood backing 2, -to which the sheet material 3 is to be secured, or both of said surfaces, and the materials preferably united under sufficient pressure to bring said materials into intimate'contact with each other. When the adhesive is of the type which includes a solvent or other liquid vehicle, suiiicient heat may be used to evaporate said solvent or liquid vehicle. In the event the adhesive is of the thermoplastic type. then sufficient heat should be employed to render said adhesive tacky.

The ply-wood backings are made in the usual manner of making ply-woods except that the various plies are arranged so that the grains thereof will run at the desired angles. To produce discs of the form shown in the drawing, the sheet material 3 and the ply-wood backing 2 maybe preformed into the desired shape and then processed and treated as previously described. Alternatively, the opposite sheet material may be formed in continuous lengths,v from which discs ofthe desired dimensions may be punched, stamped or otherwise cut.

Though the specific description herein set forth relates to composite abrasive discs, it is to be understood that the invention is not restricted thereto, since the principles thereof may be equally applied to sheets, belts, strips, etc.

Since it is obvious that various changes and modifications may be made in the above description without departing from the nature or- .spirit thereof, this invention is not restricted thereto except as set forth in the appended claims.

I claim:

1. A composite abrasive disc element comprising a ply-wood backing, a sheet material having one surface adhesively secured to said backing, and abrasive grit adhesively secured to the other surface of said sheet material, said disc element being sufficiently stiff so` that it will lie flat and sufficiently resilient and fiexible so that it will permit appreciable distortion without breaking.

2. A composite abrasive disc element comprising a ply-wood backing, a sheet material having one surface adhesively secured to said backing, and abrasive grit adhesively secured to the other surface of said sheet material, said ply-wood backing being formed of a plurality of plies so disposed with respect to each other that the grain of each -ply is at an angle to the other. said disc element being sufficiently stiff so that it will lie flat and sufficiently resilient and flexible so that it will permit appreciable distortion without breaking.

3. A composite brasive disc element comprising a ply-wood backir1ga sheet material having one surface adhesively secured to said backing, and abrasive grit adhesively secured to the other surface of said sheet material, said ply-wood backing being formed of two plies so disposed with respect to each other that the grain of one ply is at an angle of approximately to the grain of the other ply, said disc element being sufficiently stiff so that it will lie flat and sumciently resilient and flexible so that it will permit appreciable distortion without breaking.

4. A composite abrasive disc element comprising a ply-wood backing, a sheet material having one surface adhesively secured to said backing, and abrasive grit adhesively secured to the other surface of said sheet material, said plywood backing being formed of three plies so disposed with respect to each other that the grains ing a ply-Wood backing of a thickness not in exof adjacent plies are at angles of approximately 60 to each other, said disc element being sufficiently stiff so that it will lie flat and sufficiently resilient and fiexible so that it will permit appreciable distortion Without breaking.

5. A composite abrasive disc element comprising a ply-Wood backing, a sheet material having I one surface adhesively secured to said backingv one surface adhesively secured to said backing by means of an animal glue, and abrasive grit adhesively secured to the other surface of said sheet material, said ply-Wood backing being formed of a plurality of plies so disposedwith respect to each other that the grain of each ply is at an angle to the other, said disc element being sufiiciently stiff so that it will lie flat and sufficiently resilient and fiexible so that it will permit appreciable distortion Without breaking.

'7. A composite abrasive disc element comprising a ply-Wood backing, a sheet material having one surface adhesively secured to said backing by means of an animal glue, and abrasive grit adhesively secured to the other surface of said sheet material, said ply-wood backing being formed of two plies so disposed with respect to each other that the grain of one ply is at an angle of approximately 90 to the grain of the other ply', said disc element being sufficiently stiff so that it will lie fiat and sufficiently resilient and iiexible so that it will permit appreciable distortion Without breaking.

8. A composite abrasive disc element comprising a ply-wood backing, a sheet material having one surface adhesively secured to said backing by cess of approximately .045 of an inch, a sheet material formed of fabrichaving one surface thereof adhesively secured to one surface of said backing, and abrasive grit adhesively` secured to the other surface of said sheet material, said disc element being sumciently stiff so that it will lie flat and sufficiently resilient and flexible so that it will permit appreciable distortion without breaking.`

10, A composite abrasive disc element comprising a ply-Wood1 backing of a thickness not in excess of approximately .045 of an inch, a sheet material formed of fabric having one surface thereof adhesively secured to one surface of said backing, and abrasive grit adhesively secured to the other surface of said sheet material, said plywood backing being formed of a plurality of plies so disposed with respect to each other that the grain of each ply is at an angle to the other, said disc element being sufficiently stiff so that it will lie flat and sufficiently resilient andflexible so that it will per'mit appreciable distortion Without breaking.

11. A composite abrasive disc element comprising a ply-Wood backing of a thickness not in excess of approximately .045 of an inch, a sheet material formed of fabric having one surface thereof adhesively secured to one surface of said back# ing, and abrasive grit adhesively secured to the other surface of said sheet material, said plywood backing being formed of two plies so disposed With respect to each other that the grain of one ply is at an angle of approximately 90? to the grain of the other ply, said disc element being sufficiently stiff so that it will lie fiat and sufficiently resilient and flexible so that it will permit 4 appreciable distortion without breaking.

three plies sov disposed with respect to each other that the grains of adjacent plies are at angles of approximately 60 to eachother, said disc el`e` l2. 'A composite abrasive disc element comprising av ply-Wood backing of a thickness not in ex-` cess of approximately .045 of an inch, a sheet ma- NIILO HOLMSTEN. 

